The mounting of a vehicle tire on its wheel rim may result in an inadequate circular contact between both tire beads and the respective rim flanges. Such inadequate or non-uniform contacts impair the desired or required true and balanced running characteristic of the respective tire. Furthermore, wheels with an initially inadequate tire seating may assume an improved or proper seating after actual use on the road. However, such self-seating if it takes place at all, sometimes requires a substantial distance of travel before the rotating motion of the tire properly positions the two tire beads between the respective rim flanges. This self-seating, however, although desirable from one point of view, is not desirable because it can adversely influence the wheel balance. In other words, the balancing of the wheel that takes place after the tire has been mounted on a rim, is disturbed by such self-seating or re-seating of the tire on the wheel rim. As a result, it would become necessary to perform a further balancing operation following a certain distance travelled. is known from German Patent Publication DE 3,442,561 C2 (Johannes), published on May 22, 1986, to improve the seat of a tire on its rim by an apparatus which is employed directly after mounting the tire on the rim. Johannes discloses to inwardly press the flank surfaces of the tire by two pressure rings with a force directed parallel to the rotational wheel axis. The axial force is applied radially outwardly of the wheel flange to such an extent that the lateral outer bead surfaces of the tire are slightly lifted off the respective wheel flange while the inwardly positioned tire bead surfaces remain in contact with the wheel rim and wheel rim flange. This force application is intended to cause the bead surfaces of the tire to fit precisely into the recesses provided in the area of the rim flanges. In the known apparatus the diameters of the pressure rings are adapted to an average diameter of the tire side surfaces of the particular wheel or tire type. This feature has the disadvantage that for each wheel type with different average tire flank surface diameters another apparatus is required or it is necessary to exchange the pressure application rings against other rings with different diameters.
German Patent Publication 2,333,057 (Kappel et al.), published on Jan. 16, 1975 discloses a method and apparatus for reducing radial and/or lateral or axial unbalances of vehicle wheels. Kappel et al teach in their method that an air-filled tire on a wheel is pressed axially along its flanks or side walls by a pressure ring to such an extent that the tire beads are lifted off the rim flanges to release the air, whereupon the rim and the tire are rotated relative to each other and then the tire is again filled with air. In the known apparatus the wheel is mounted on a rotatable clamping head while the pressure application ring is mounted also on a rotatable head opposite the wheel carrying head. The pressure application ring on one flank of the tire cooperates with a counter tool that is pressed against the other or opposite tire flank. The cooperation of these two tools, namely the ring and the counter tool sufficiently remove the tire beads from the rim flanges so that air can escape from the tire. The clamping head or the opposite mounting head are rotatable so that either the rim or the tire or both are rotatable relative to each other by a respective drive. A pressurized air tank is provided to refill the tire after the adjustment has been made. Such an apparatus also leaves room for improvement, especially with regard to the possibility of handling various tire sizes on the same machine.